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pcat: separate MBR code and OS code

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MBR code now strictly loads OS code into memory and jumps into it.

Now, I've got to consolidate my assembler code, modrm logic is
messed up.
This commit is contained in:
Virgil Dupras 2020-06-13 15:35:16 -04:00
parent e17f2e6907
commit 07e50313c7
6 changed files with 31 additions and 11 deletions
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1
blk/753
View File

@ -4,6 +4,7 @@
: INT, 0xcd A, A, ;
( no argument, flow ops are special )
: JMP8, 0xeb A, ; : JMP16, 0xe9 A, ; : JZ, 0x74 A, ;
: JMPr, 0xff A, 7 AND 0xe0 OR A, ;
: LODSB, 0xac A, ; : CLI, 0xfa A, ; : HLT, 0xf4 A, ;
: STI, 0xfb A, ;
: ORrr, 0x08 A, MODRMrr A, ;

11
blk/811
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@ -2,14 +2,9 @@ H@ ORG ! 0x7c00 BIN( ! ( BIOS loads boot bin at 0x7c00 )
JMP8, L1 FWR8 ( start )
ORG @ 0x25 + HERE ! ( bypass BPB )
L1 FSET ( start )
CLI, CLD, AX AX XORxx, DS AX MOVsx, ES AX MOVsx, STI,
CLI, CLD, AX AX XORxx, DS AX MOVsx, ES AX MOVsx,
SS AX MOVsx, SP 0xffff MOVrI, STI,
AH 2 MOVri, DX 0 MOVrI, CH 0 MOVri, CL 2 MOVri, AL 1 MOVri,
BX 0x8000 MOVrI, 0x13 INT, ( read 2nd sector of boot floppy )
SI 0x8000 MOVrI, AH 0x0e MOVri, ( print char )
L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
JZ, L2 FWR8 ( next ) 0x10 INT, ( print char )
JMP8, L1 ( loop ) BWR
L2 FSET ( next ) AH 0 MOVri, 0x16 INT, ( read kbd )
AH 0x0e MOVri, 0x10 INT, ( spit read char ) HLT, ( done )
BX JMPr,
ORG @ 0x1fe + HERE ! 0x55 A, 0xaa A,
," Hello from 2nd sector of boot floppy!" 0 A,

10
blk/812 Normal file
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@ -0,0 +1,10 @@
H@ ORG ! 0x8000 BIN( !
JMP8, L1 FWR8 ( start )
L2 ( msg ) BSET ," Hello World!" 0 A,
L1 FSET ( start )
SI L2 @ ( msg ) MOVrI, AH 0x0e MOVri, ( print char )
L1 BSET ( loop ) LODSB, AL AL ORrr, ( end of str? )
JZ, L2 FWR8 ( next ) 0x10 INT, ( print char )
JMP8, L1 ( loop ) BWR
L2 FSET ( next ) AH 0 MOVri, 0x16 INT, ( read kbd )
AH 0x0e MOVri, 0x10 INT, ( spit read char ) HLT, ( done )

14
recipes/pcat/Makefile
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@ -1,16 +1,26 @@
TARGET = boot.bin
TARGET = disk.bin
BASEDIR = ../..
EDIR = $(BASEDIR)/emul
STAGE = $(EDIR)/stage
.PHONY: all
all: $(TARGET)
$(TARGET): xcomp.fs $(STAGE)
mbr.bin: mbr.fs $(STAGE)
cat mbr.fs | $(STAGE) > $@
os.bin: xcomp.fs $(STAGE)
cat xcomp.fs | $(STAGE) > $@
disk.bin: mbr.bin os.bin
cat mbr.bin os.bin > $@
$(STAGE):
$(MAKE) -C $(EDIR) stage
.PHONY: emul
emul: $(TARGET)
qemu-system-i386 -fda $(TARGET)
.PHONY: clean
clean:
rm *.bin

4
recipes/pcat/mbr.fs Normal file
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@ -0,0 +1,4 @@
750 LOAD
811 LOAD
ORG @ 256 /MOD 2 PC! 2 PC!
H@ 256 /MOD 2 PC! 2 PC!

2
recipes/pcat/xcomp.fs
View File

@ -1,4 +1,4 @@
750 LOAD
811 LOAD
812 LOAD
ORG @ 256 /MOD 2 PC! 2 PC!
H@ 256 /MOD 2 PC! 2 PC!